Compressor unloader



11, 1934; v c. s'. 4BAKER 1,984,171

GOMPRES SOR UNLOADER Filed Oct. 20, 1952 INVENToR.- (Zad edfm'en BY y H15 ATTORNEY Patented Dec. 11, 19344 UNITED STATES PATENT OFFICE l coMrnEssoa UNLoAnr-:n Charles S. Baker, Corning', N. I., assignor to Ingersoll-Rand Company, Jersey City, N. J., a corporation of New Jersey. Application October Zi), 1932, Serial No. 638,750 7 Claims. .(Cl. 2313-25) This invention concerns unloading systems for compressors and more particularly a system for proportional unloading by holding the intake valve of the compressor open for a greater or lesser period of the compression stroke of the piston. In order to accomplish this result it is proposed to connect the receiver to pressure actuated valve litters o1' a common type adapted to hold the inletl valves in open position. A pres- 10 sure fluidv control valve in theline between the receiver and the valve litters prevents operation of the latter until pressure in the receiver has been built up to a predetermined point.

A timing device inserted in the pressure line between the control valve and valve lifter intermittently opens the connection in the pressure line and then closes it simultaneously opening a relief port whereby pressure behind the valve litter may be exhausted to atmosphere. Pressure actuated means responsive to receiver pressures are connected to the timing device or' controller toladvance or retard the period o! operation of the valve lifter.

It is an object of theinvention to .provide means for the proportional unloading of a compressor by interference with the normal action of the valves during a greater or lesser portion of the piston cycle as the situation requires.

i This interference consists of holding the inlet A valve'open during part of the compression stroke so that, in eect,'the compressor is short stroked and a smaller volume of iluid is supplied to the receiver. It is the purpose oi the invention to make such interference with the normal valve 35 action beginV at a predetermined receiver pressure and to increase as the pressure increases. By increase o! interferenceis meant the prolonging oi the period oi the compression stroke during which normal operation is suspended.

The construction and operation of the proportional unloading device above mentioned may be more readily understood by reference to the accompanying drawing in which,

Fig. 1 represents a somewhat'diagrammatic side view of a reciprocal compressor in which the compressor cylinder is shown-in section. l

Fig. 2 is a sectional view o! the timing device and its pressure actuated control, and

Fig. 3 is another sectional -view o'f the timing f devicetakenon theline3-3 of Fig.2 and looking in the direction of vthe arrows. Referring to the drawing, a compressor cyl inder designated generally by 5 is provided with a piston chamber 6 in which reciprocates a pis- 65 ton 7 having a piston rod 9 connectedby a con'- compressor of the reciprocating type provided with the usual inlet and exhaust valves and adapted to' discharge into a storage tank or receiver. In this standard equipment it is propsed to nt theinlec valves 15 with valve meters 15 29. The valve'lifters 29 are of a well known type,

f commonly referred to as free air unloaders. They consist of afork '31 adapted to bear upon the valve and to hold it oil its seat. The shank oi' the fork 31 is aixed to a plunger 33 which is 20 slidable in a bore 35 in a valve cap 37. Pressure fluid to actuate the plunger 33 is admitted to the bore 35 through the valve cap 37 by suitable connections 39.

Mounted on a bracket 41 on the compressor casing 8 is a sylphon 43 the interior of which is suitably connected to the receiver 27 by a conduitei'v.` The sylphon'is connected by a rod 47 to the short arm of the lever 49 which is pivoted to the end oi an upturned extension 51 of the 30 bracket 41. e f

Inserted in a pipe 53 is a pressure operated `valve 55 which is adapted to open when a predetermined pressure is attained in the receiver 27. In the present application the-pipe 53 is :fittedv 35 with branch arms 54 which lead into a distributor or controller generally designated as 57 which is suitably moimted upon the casing 8. Pipes 56 lead from connections on the distributor to connections 39 on the iree air unloaders. .qu

Keyed to a shait59 of an engine (not shown) is a gear wheel 61 which is connected by a chain 63 to a similar gear wheel 65 upon the controller 57 so that the distributor may be` driven in synchronism with the compressor. 45

A link 67 connects the lever arm 49 to a lug 69 on the distributor 57 to permit automatic ade justment of the latter. A spring 71 supported by the extension 51 and provided with an adjust# ment 73 bears against the arm 49 inopposition 5u The apparatusthus far described is a simple 1.0V

79 to one of which is attached the'gear wheel 65. The shafts 79 may be jcurnalled in bearings 81 supported by arms of e. support frame 83. The casing 77 is fitted with a cover plate 78 so that it completely encloses the valve 75. y

The pipes 54 and 56 are connected to appropriate apertures in the casing 77. For the purpose of maintaining balance the pipes 54 in the present instance enter the casing 77 at points approximately 180 apart, but in order to avoid interference they are laterally spaced from each other. Similarly the pipes 56 are connected to the stator 77 in such a manner that each pipe 56 is in the same plane as its corresponding pipe 5d. 'Ihe cylindrical valve or rotor is provided with parallel peripheral slots S5 in order that com municaton between each pipe 5e and its mate 56 may be established at 186 intervals of crankshaft rotation.

In the casing 77 and in alignment with each pair of pipes 54 and 56 are exhaust ports 58 which are adapted to open communication upon rotation of the valve 75 between the pipes 56 and the outside atmosphere thereby permitting pressure fluid from the back of the plungers 33 to escape through the pipes 56 and their appropriate valve slots to atmosphere.

During the operation of the compressor the timing device or controller 57 is continually in operation, but no uid may pass through it andit performs no useful function until the receiver pressure reaches a point where the valve 55 is lopened and pressure iluid passes from the receiver 27 through the pipes 54. It may be notedhere that the pipes 54 and 56 are all tted with flexible sections 60 at the stator connection to permit limited rotation -of the casing 77 in response to movement of the link 67.

Rotation of the casing 77 is automatically provided by the sylphon through the linkage 47, t9 and 67 acting upon the lug 69 which extends from the casing 77. When the4 receiver pressure inside the sylphon is suiiicient to overcome the resistance of the spring'71 the sylphon e and raises the short arm of the lever 49 and de= presses the long arm, which acts through the link 67 upon the lug 69, thereby forcingthe casing 77 to turn in a counter-clockwise direction which has the effect of retarding (with respect to the compressor cycle) the exhaust from the pipe 56 through the outlets 58, whereby the valve 15 is maintained 'in open position during a portion of--the compression stroke of the piston 7. The operation of the device may be brieiiy summarized as follows: l

The crankshaft59 and its attached toothed wheel 61 rotate in a counter-clockwise direction and this rotation is communicated through the chain 63 and the gear wheel 65 to the rotary valve 75. Y

Rotation of the crankshaft also causes recipr'ocation of the piston 7 in piston chamber 6. Each stroke of the piston compresses air on one side thereof and sucks air into the piston chamber on the other side thereof. The inlet and exhaust valves open and close automatically in response to pressure changes in the piston chamber caused 'by movement of the piston.

lair pumped bythe compressor is forced into the receiver 27'where itsv pressure' is increased. After the pressure reaches a predetermined point limited by the resistance of the valve 55 air from the receiver flows to the controller 57 as previously described. At a point in the compression cycle just after an intake valve has opened the slot 85 of the rotor opens communication between a pipe 54 and a pipe 56. Air at receiver pressure then flows to the valve lifter 29 and operates it as hereinbefore set forth. The pressure behind the valve lifter holds the inlet valve open until the slot 85 has closed communication with pipe 5e and established communication with the exhaust port 58 which action is timed to be somewhat later than the normal time of automatic closing of' the inlet valve. Air is then exhausted from the valve lifter and the inlet valve closes permitting compression during the remainder of the piston stroke. This tardy closing oi' the valve reduces the pumping power of the compressor and results in a slower increase 'of pressure in the receiver.

vssg that pressure continues to build up in the receiver the communicated pressure within the sylphon'then causes this instrument to expand overcoming the resistance of the spring 7l. Expansion of the sylphon working through its connecting linkage causes a limited counterclockwise movement of the casing 77. As' the casing moves counterclockwise all of the pipe connections and exhaust ports are retarded with respect to the crankshaft position and consequently with respect to the period of piston travel. 'I'he action of the valve lifters 29 are consequently retarded and the inlet valves 15 are held open for a longer period of the compression stroke. It will be seen that the interference with normal valve action may be made to vary in proportion to the pressure Iin the receiver.

Having thus described my invention I do not desire to be limited to the speciiic structure disclosed but claim:

1. In a compressor, a cylinder, a piston reciprocable therein, automatic inlet valves normally opened and closed in response to pressures created by reciprocation of the piston, a receiver for pressure fluid discharged by the compressor, individual pressure responsive means for each iniet valve to delay automatic closing of the inlet valve until the piston has traveled through part of its compression stroke, and a rotary distributing device responsive to' receiver pressure to control the distribution of pressure fluid to the said means and thus the duration of said delay.

2. In a compressor, a cylinder. a piston re?- ciprocable therein, automatic inlet valves normally opened and closed in response to pressures created by reciprocation of the piston, individual pressure responsive means for each inlet valve to delay automatic closing of the inlet valve until the piston has traveled through part of its compression stroke, and means comprising a rotary timing device responsive to fluid pressure to regulate the admission of pressure fluid to the first said means and thus the period of delay.

3. In a compressor, a. cylinder, a piston reciprocable therein, an inlet and an outlet valve, a receiverfor pressure fluid, means controlled by uid pressure for holding the inlet valve open during part of the compression stroke of the piston, a rotary timing device operating synchronously with the compressor piston for admitting pressure iluid to the valve holding means, and means responsive to pressure in the receiver to control the action of said timing device to advance or delay with respect to the cycle of the piston the time of admission of pressure fluid to the valve holding means.

4. In a compressor, a cylinder, a piston .re-

ciprocabie therein, an inlet and an outlet valve in thecylinder, areeeiveriorpressure iluiddischarged lfrom the compressor. individual pressure responsive means for each inlet valve for holding the inlet valve open during part of.` the compression stroke of the piston, and means comprising arotary distributor responsive to receiver pressure to regulate the ilow of pressure iluid to the pressure responsive meansand thus control the duration of opening oi the inlet valve during the compression stroke.

5.- In a compressor, a cylinder, a piston reciprocable therein, an inlet and an outlet valve for the cylinderr a receiver for pressure fluid discharged from the compressor, pressure iluid means to hold the inlet valve open during part 'of the compression stroke of the piston, a prime bore, a distributor interposed in the conduit to controltheiiowofpressureiluidto and from the valve lifter in a timed cycle of operations, said distributor having a Vstator element provided with a connection to a source of pressure fluid, a connection to the valve litter bore and a vent to the atmosphere, and a rotor in-the stator rotating in iixed relationship to the compressor piston and having a peripheral slot which successively opens communication between the pressure source connection and the valve litter connection and between the valve lifter connection and the atmospheric vent.

7. In combination with a compressor and the like, a cylinder, a piston, an inlet and an exhaust valvein the cylinder, a pressure actuated valve lifter attached to a plunger reciprocable in a bore, a conduit to admit pressure uid into the bore, a distributor interposed in the conduit to control the flow of pressure fluid to and from the valve litter in a timed cycle of operations, said distributor having a stator element provided with a connection to a source of pressure iluid, a connection to the valve lifter bore and a vent tothe atmosphere, a rotor in the stator rotating in ilxed relationship to the compressor piston and having a peripheral slot which successively opens communication between the pressure source connection and the valve lifter connection and between the valve lifter connection and the atmos-y pheric vent, and means to adjust the stator with respect to the rotor to change the time relationship between the valve litter and the piston.

CHARLES S. BAKER. 

